Analysis method of absolute energy efficiency and relative energy efficiency of compressed air system

Abstract

An analysis method of absolute energy efficiency and relative energy efficiency of the compressed air system. For the compressed air system operating in a form of a single compressor, a gas flow rate and a corresponding operating power of the compressor operating in the single compressor model are measured under a specified flow rate. Meanwhile, influencing factors of the compressor operation are monitored. The absolute energy efficiency of the compressor is defined, and a curve of the absolute energy efficiency of the compressor varying with the operating time versus the above factors are plotted in a same coordinate system. Obtaining absolute energy efficiency data of the compressor in a corresponding state. By analyzing the absolute energy efficiency under corresponding conditions and based on the corresponding chart, the actual unit consumption of a given single compressor and its changing rule under different production and environmental operating conditions can be intuitively analyzed.

Claims

1. An analysis method of an absolute energy efficiency of a compressed air system operating in a single compressor mode, comprising following steps: (1) measuring a gas flow rate Q.sub.i and a corresponding operating power N.sub.i of a compressor operating in the single compressor mode under a value state of a specified gas flow rate; and at the same time, monitoring influencing factors of the compressor on operation, the influencing factors comprising: an intake port temperature, a humidity, an atmospheric pressure, an effective pressure after a filter, a discharge pressure, and an effective pressure ratio; (2) defining the absolute energy efficiency of the compressor as follows: ${\eta }_{\mathrm{Ai}}=\frac{N_i}{Q_i}$ in which η.sub.Ai is a value of a real-time absolute operating energy efficiency of a single compressor numbered i; N.sub.i is the operating power of the single compressor, in kW; and Q.sub.i is the gas flow rate of the single compressor, in m.sup.3/min; and plotting a curve of the absolute energy efficiency of the compressor varying with an operating time versus the above influencing factors in a same coordinate system; (3) according to a standard gas state defined by a user, combined with monitoring results of the influencing factors, correcting an influence on the absolute energy efficiency of the compressor to obtain an absolute energy efficiency data of the compressor in a corresponding state; (4) optimizing operation of the compressor based on the absolute energy efficiency data of the compressor.

2. An analysis method of an absolute energy efficiency of a compressed air system operating in an air compressed station mode, comprising following steps: (1) obtaining a corrected absolute energy efficiency data of each single compressor in the compressed air station according to the method of claim 1; (2) averaging the absolute operating energy efficiency of each single compressor numbered i in a specified period: $\stackrel{\_}{{\eta }_{\mathrm{Ai}}}=\frac{\underset{i}{.Math.}{\eta }_{\mathrm{Ai}}}{M_i}$ in which η.sub.Ai is an average value of all sampled specific powers of the compressors numbered i in the specified period; η.sub.Ai is the value of the real-time absolute operating energy efficiency of the compressor numbered i; and M.sub.i is a total sampling number for the compressor numbered i in the specified period; and (3) constructing an absolute energy efficiency model of the air compressed station in the specified period, with a proportion of an operating time of different compressors in the specified period as a weight: ${\eta }_{\mathrm{AS}}=\underset{i}{.Math.}\frac{t_i}{t}\stackrel{\_}{{\eta }_{\mathrm{Ai}}}$ in which: η.sub.As is the absolute energy efficiency of the air compressed station in the specified period; t is a value of the specified period, in h; t.sub.i is the operating time of the compressor numbered i in the specified period, in h.

3. An analysis method of a relative energy efficiency of the compressed air system operating in a single compressor mode, comprising following steps: (1) obtaining a corrected absolute energy efficiency data of the single compressor in the air compressed station according to the method of claim 1; and (2) calculating a relative energy efficiency of the single compressor based on the absolute operating energy efficiency according to characteristics of a given compressor: ${\eta }_{R1i}=\frac{{\eta }_{\mathrm{DAi}}}{{\eta }_{\mathrm{Ai}}}100\%$ in which: η.sub.R1i is the relative operating energy efficiency data of a single compressor numbered i obtained according to the characteristics of the given compressor; η.sub.Ai is the value of a real-time absolute operating energy efficiency of the single compressor numbered i; and η.sub.DAi is a correspondingly designed absolute operating energy efficiency of the single compressor numbered i under current operating conditions.

4. An analysis method of a relative energy efficiency of a compressed air system operating in an air compressed station mode, comprising following steps: (1) obtaining the relative energy efficiency data of each single compressor in the air compressed station according to the method of claim 3; (2) averaging the relative operating energy efficiency of each single compressor numbered i in a specified period: $\stackrel{\_}{{\eta }_{R1i}}=\frac{\underset{i}{.Math.}{\eta }_{R1i}}{M_i}$ in which, η.sub.R1i is an average value of the relative operating energy efficiency of the single compressor numbered i in the specified period obtained according to given compressor characteristics; η.sub.R1i is the relative operating energy efficiency of the single compressor numbered i obtained according to the given compressor characteristics; and M.sub.i is a total sampling number for the compressor numbered i in the period; and (3) constructing a relative energy efficiency model of the air compressed station in the specified period, with a proportion of an operating time of different compressors in the specified period as a weight: ${\eta }_{\mathrm{RS}1}=\underset{i}{.Math.}\frac{t_i}{t}\stackrel{\_}{{\eta }_{R1i}}$ in which: η.sub.RS1 is the relative energy efficiency of the air compressed station in the specified period; t is a value of the specified period, in h; and t.sub.i is the operating time of the compressor numbered i in the specified period, in h.

Description

DETAILED DESCRIPTION

(1) Aiming at a complex compressed air system, an operating energy efficiency analysis mechanism for a single compressor and/or an air compressed station is established, and a corresponding mathematical model of the energy efficiency analysis is established. Firstly, rather than a traditional energy efficiency analysis mechanism, a concept of absolute energy efficiency analysis and relative energy efficiency analysis is proposed.

(2) 1. Absolute Operating Energy Efficiency Analysis

(3) The absolute energy efficiency analysis mechanism is divided into two parts, one is the absolute operating energy efficiency analysis of a single compressor; and the other is, on a basis of the single compressor analysis, to take characteristics of the single compressor operating time into account to make the absolute operating energy efficiency analysis for the whole air compressed station. A basic idea and model are as follows:

(4) 1) Absolute operating energy efficiency analysis for a single compressor

(5) For the compressor in operation, no matter what type of the compressor is, a gas flow rate Q.sub.i(m.sup.3/min) (under a value of a specified gas flow rate) is measured under current operating conditions and a corresponding operating power N.sub.i (kW) were measured at the same time, and the absolute energy efficiency of the compressor was defined as:

(6) ${\eta }_{\mathrm{Ai}}=\frac{N_i}{Q_i}$

(7) Its value represents a value of real-time specific power under its operating conditions and the data table of GB19153 can be used to judge its operating energy efficiency grade, which can be modeled to establish a different database to judge the operating specific power under a corresponding pressure, compare it with different energy efficiency grade standards, and show direct results. This parameter lacks consideration of real-time and historical trend monitoring and analysis in actual operations.

(8) Instead of the traditional specific power analysis concept, it is further required in the present disclosure to monitor the intake port temperature, the humidity, the atmospheric pressure, the effective pressure after the filter, the discharge pressure and the effective pressure ratio so that a curve of the absolute energy efficiency of the compressor varying with the operating time versus the above factors are plotted in a same coordinate system, which are represented with different color curves together with absolute energy efficiency at a same interface, in which the corresponding ordinate can be used to analyze the influence of various factors on the absolute operating energy efficiency and lay a foundation for a single factor analysis, which is not the same as any type of monitoring and analysis in the traditional mechanisms.

(9) For example, the influence of the inlet temperature, the humidity and the pressure on the absolute energy efficiency analysis can be made on a basis of a large number of monitored data with the absolute energy efficiency as the ordinate and environmental parameters at different sampling times as the abscissa, to construct a data curve, in this way, the influence of various factors on the absolute energy efficiency at the corresponding time and under given machine conditions can be directly determined. The influence of these factors on the compressor operating characteristics can be objectively shown, and the influence of the environmental operating conditions and the production load intensity on the absolute energy efficiency under a same inlet guide vane (IGV) and blow off valve (BOV) opening and/or closing degree can be revealed.

(10) 2) Overall absolute energy efficiency analysis for the air compressed station in a certain period

(11) With different compressor types and manufacturers for the air compressed station, a time analysis is added to each compressor in operation. For different machines operating in a specified period, the absolute operating energy efficiencies of respective single compressors are averaged firstly in a numbered order:

(12) $\stackrel{\_}{{\eta }_{\mathrm{Ai}}}=\frac{\underset{i}{.Math.}{\eta }_{\mathrm{Ai}}}{M_i}$

(13) Here:

(14) η.sub.Ai—an average value of all sampled specific powers of the compressors numbered i in the specified period;

(15) η.sub.Ai—a real-time absolute operating energy efficiency of the compressor numbered i;

(16) M.sub.i—total number of samples of the compressor numbered i in this period.

(17) The above formula gives the average value of the absolute operating energy efficiency of the compressor numbered i in the specified period.

(18) An absolute energy efficiency model of the air compressed station in the specified period, with a proportion of operating time of each equipment in the specified period as a weight, can be constructed:

(19) ${\eta }_{\mathrm{AS}}=\underset{i}{.Math.}\frac{t_i}{t}\stackrel{\_}{{\eta }_{\mathrm{Ai}}}$

(20) Here:

(21) η.sub.AS—the absolute energy efficiency of the air compressed station in the specified period;

(22) t—a value of the specified period (h);

(23) t.sub.i—the operating time of the compressor numbered i in the specified period (h);

(24) The model considers the overall absolute operating energy efficiency of the same air compressed station with different operating compressors. And an advantage of this model is to clarify changes of the absolute operating energy efficiency in different operating compressor combinations in different periods.

(25) 2. Relative Operating Energy Efficiency Analysis

(26) As mentioned above, the energy efficiency analysis of the whole air compressed station should consider two modes: a single compressor model and a station model. Although the absolute energy efficiency is intuitive, its problem is also obvious, that is, the operating conditions of the compressors vary, and the absolute operating energy efficiency inevitably changes under different operating conditions, the absolute energy efficiency cannot be directly linked with the changes of operating conditions. Under different operating conditions, the isothermal cooling effect is the optimal power consumption of a compressed air system, which is only linked with the compression process and the waste heat utilization is not considered. On this premise, the relative operation energy efficiency analysis models for the single compressor and the overall air compressed station are constructed as follows:

(27) 1) Relative operating energy efficiency analysis for the single compressor

(28) The relative operating energy efficiency model is still first developed for the single compressor, and the model has two meanings, one is based on the absolute operating energy efficiency model and according to the characteristics of a given compressor; and the other is to take isothermal cooling power as a reference, the two efficiency models are as follows

(29) ${\eta }_{R1i}=\frac{{\eta }_{\mathrm{DAi}}}{{\eta }_{\mathrm{Ai}}}100\%$

(30) Here:

(31) η.sub.R1i—the first type of relative operating energy efficiency of the compressor numbered i;

(32) η.sub.Ai—the value of a real-time absolute operating energy efficiency of a single compressor numbered i;

(33) η.sub.DAi—the correspondingly designed absolute operating energy efficiency of the compressor numbered i under current operating conditions.

(34) The meaning of the first type of relative operating energy efficiency is a degree to which the operating specific power under the current operating condition (including an opening degree of an inlet guide vane and/or a BOV) deviates from that under the high-efficiency operating condition. For all compressors, the designed specific power is the optimal value, and with the compressor operating, its characteristics will inevitably decline, which should be based on the design parameters of the compressor itself. The first type of relative operation energy efficiency analysis can be used as a data benchmark for health diagnosis and operation maintenance. If it can be determined that the first type of relative operating energy efficiency is lower than 80% (a specific threshold can be determined according to the actual situation), the operation maintenance is required to be made to the compressor.

(35) Corresponding to the first type of relative operating energy efficiency model for the single compressor, for each operating condition (inlet and outlet pressure, pressure ratio, temperature, humidity, flow rate, IGV/BOV), under the corresponding pressure, pressure ratio and flow rate, and with the isothermal cooling effect as a benchmark, the second type of relative operating energy efficiency model for the single compressor is established as follows:

(36) ${\eta }_{R2i}=\frac{16.67\times P_{\mathrm{Xi}}\times Q_i\times \ln \left(\left(P_{\mathrm{Oi}}+P_{\mathrm{Xi}}\right)\right)\text{/}{\eta }_{\mathrm{Mi}}}{N_i}100\%$

(37) Here:

(38) η.sub.R2i—the second type of relative operating energy efficiency of the compressor numbered i;

(39) P.sub.Xi—an effective suction pressure after a filter at an inlet of the compressor of the compressor numbered i, in MPa;

(40) Q.sub.i—a displacement of the compressor numbered i under a specified state, in m.sup.3/min;

(41) P.sub.0i—a measured discharge pressure of the compressor numbered i, in MPa;

(42) η.sub.Mi a conversion efficiency of the motor of the compressor numbered i under a load rate corresponding to the isothermal cooling shaft power;

(43) N.sub.i—a measured operating power of the compressor numbered i under current conditions, in kW.

(44) As shown in the formula, different from the definition from GB50029, the second type of relative operating energy efficiency model for the single compressor is a value varying with time, and the pressure, the flow and the power are all instantaneous values, and in this way, there is no contradiction between instantaneous and average concepts, and additionally the motor characteristics are combined, which is more reasonable. The first kind of relative operating energy efficiency is to analyze a relative change of the absolute operating energy efficiency under given designed characteristics; and rather the second kind of relative operating energy efficiency is to analyze all operating conditions under benchmarking of the isothermal cooling, and design differences of different machines are implied in a value of actual operating power. The benefit of this model is that the effective suction pressure and pressure ratio are included (the effective suction pressure refers to the effective inlet pressure after the filter).

(45) 2) Overall relative operating energy efficiency model for the air compressed station in a specified period

(46) Based on the two types of operating energy efficiency models for the single compressor, considering the proportion of the operating time of a respective single compressor in a specified period, and based on the statistical average of the instantaneous value of the relative operating energy efficiency, the relative operating energy efficiency models for the whole air compressed station are constructed as follows:

(47) First type of relative operating energy efficiency model for the air compressed station

(48) ${\eta }_{\mathrm{RS}1}=\underset{i}{.Math.}\frac{t_i}{t}\stackrel{\_}{{\eta }_{R1i}}$

(49) Second type of relative operating energy efficiency model for the air compressed station

(50) ${\eta }_{\mathrm{RS}2}=\underset{i}{.Math.}\frac{t_i}{t}\stackrel{\_}{{\eta }_{R2i}}$

(51) The above two formulas introduce the weight of each single compressor based on the proportion of its operating time, and the average of the first and second types of relative operating energy efficiency of different machines in the corresponding period.

(52) $\stackrel{\_}{{\eta }_{R1i}}=\frac{\underset{i}{.Math.}{\eta }_{R1i}}{M_i}$$\stackrel{\_}{{\eta }_{R2i}}=\frac{\underset{i}{.Math.}{\eta }_{R2i}}{M_i}$

(53) Through the above-mentioned energy efficiency model, the overall operation energy efficiency of each compressor in operation and even of the whole air compressed station can be analyzed in real-time and historically, which can directly lay a foundation for operation, maintenance, optimization and health diagnosis.