scholarly journals Interpretation of NO<sub>3</sub>–N<sub>2</sub>O<sub>5</sub> observation via steady state in high aerosol air mass: The impact of equilibrium coefficient in ambient conditions

2021 ◽  
Author(s):  
Xiaorui Chen ◽  
Haichao Wang ◽  
Keding Lu
Keyword(s):  
Steady State ◽  
Data Sets ◽  
Ambient Conditions ◽  
Air Mass ◽  
Steady State Analysis ◽  
State Approximation ◽  
Nighttime Chemistry ◽  
Steady State Approximation ◽  
The Impact ◽  
State Analysis

Abstract. Steady state approximation for interpreting NO3 and N2O5 has large uncertainty under complicated ambient conditions and could even produces incorrect results unconsciously. To provide an assessment and solution to the dilemma, we formulate data sets based on in-situ observations to reassess the applicability of the method. In most of steady state cases, we find a prominent discrepancy between Keq (equilibrium coefficient for reversible reactions of NO3 and N2O5) and correspondingly simulated [N2O5]/([NO2]×[NO3]), especially in wintertime high aerosol conditions. This gap reveals the accuracy of Keq has a critical impact on the steady state analysis in polluted region. In addition, the accuracy of γ(N2O5) derived by steady state fit depends closely on the reactivity of NO3 (kNO3) and N2O5 (kN2O5). Based on a complete set of simulations, air mass of kNO3 less than 0.01 s−1 with high aerosol and temperature higher than 10 °C is suggested to be the best suited for steady state analysis of NO3–N2O5 chemistry. Instead of confirming the validity of steady state by numerical modeling for every case, this work directly provides concentration ranges appropriate for accurate steady state approximation, with implications for choosing suited methods to interpret nighttime chemistry in high aerosol air mass.

Steady State Analysis of a SOFC/GT Hybrid Power Plant Test Rig

2008 ◽  
Author(s):  
Tobias Panne ◽  
Axel Widenhorn ◽  
Manfred Aigner
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Ambient Conditions ◽  
Test Rig ◽  
Steady State Analysis ◽  
Pressure Losses ◽  
System Parameters ◽  
Hybrid Power Plant ◽  
Plant Test ◽  
State Analysis

In the present paper a steady state analysis of a SOFC/GT hybrid cycle test rig is shown. In the test rig the SOFC stack is replaced by a hardware simulator. Therefore the cycle can be investigated without the risk of damaging the cell. One focus of the numerical studies presented here is the influence of the SOFC stack size on the commercial Turbec T100 gas turbine and the system parameters, i.e., power output and electrical efficiency. The results are used to define the stack size for the test rig simulator. Based on the test rig configuration another focus of this paper is to work out the effect of several system parameters, like ambient conditions or pressure losses, on the hybrid system. Here the discussion will concentrate on the gas turbine operating behavior. Furthermore the power balance between fuel cell and gas turbine. Therefore the SOFC boundary conditions are changed to analyze there influence on the system performance. For the presented studies a validated steady state in-house simulation tool is used.

Analysis of Single Buffer Random Polling System With State-Dependent Input Process and Server/Station Breakdowns

2018 ◽  
Vol 9 (1) ◽  
pp. 22-50 ◽  
Author(s):  
Thomas Y.S. Lee
Keyword(s):  
Steady State ◽  
Linear Model ◽  
Repair Process ◽  
Polling System ◽  
Steady State Analysis ◽  
Relaxation System ◽  
Polling Model ◽  
State Dependent ◽  
Non Linear ◽  
State Analysis

Models and analytical techniques are developed to evaluate the performance of two variations of single buffers (conventional and buffer relaxation system) multiple queues system. In the conventional system, each queue can have at most one customer at any time and newly arriving customers find the buffer full are lost. In the buffer relaxation system, the queue being served may have two customers, while each of the other queues may have at most one customer. Thomas Y.S. Lee developed a state-dependent non-linear model of uncertainty for analyzing a random polling system with server breakdown/repair, multi-phase service, correlated input processes, and single buffers. The state-dependent non-linear model of uncertainty introduced in this paper allows us to incorporate correlated arrival processes where the customer arrival rate depends on the location of the server and/or the server's mode of operation into the polling model. The author allows the possibility that the server is unreliable. Specifically, when the server visits a queue, Lee assumes that the system is subject to two types of failures: queue-dependent, and general. General failures are observed upon server arrival at a queue. But there are two possibilities that a queue-dependent breakdown (if occurs) can be observed; (i) is observed immediately when it occurs and (ii) is observed only at the end of the current service. In both cases, a repair process is initiated immediately after the queue-dependent breakdown is observed. The author's model allows the possibility of the server breakdowns/repair process to be non-stationary in the number of breakdowns/repairs to reflect that breakdowns/repairs or customer processing may be progressively easier or harder, or that they follow a more general learning curve. Thomas Y.S. Lee will show that his model encompasses a variety of examples. He was able to perform both transient and steady state analysis. The steady state analysis allows us to compute several performance measures including the average customer waiting time, loss probability, throughput and mean cycle time.

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