Equivalent matching model of a regulated two-stage turbocharging system for the plateau adaptability

Abstract

The matching problem becomes much more difficult between a regulated two-stage turbocharging system and a diesel engine when they are required to work at different altitudes. This is mainly because there are three or even four main variables to be determined for a regulated two-stage turbocharging system, and the change in the operating altitude also extends the matching problem from a two-dimensional problem of the speed and the load to a three-dimensional problem of the speed, the load and the operating altitude. An optimal scheme for a regulated two-stage turbocharging system should be determined to optimize the plateau adaptability based on the relationship between the matching point, the desirable pressure ratio distribution and the operating altitude. Therefore, a theoretical study on matching a regulated two-stage turbocharging system to a diesel engine at different altitudes is conducted in this paper. The turbine equivalent area of a regulated two-stage turbocharging system is derived on the basis of the turbine flow characteristic model with the thermodynamics equations and the mass and energy conservation of the turbocharging system. The speed and altitude ranges are discussed with the results calculated by the proposed matching model in MATLAB software. Then the simulations with GT-Power software are carried out to validate the application of the equivalent matching model. The calculated results show that the problem of the speed range of the regulated two-stage turbocharging system at different altitudes can be converted to the speed range of a matching scheme based on different pressure ratio distributions at a constant altitude. The altitude range of the regulated two-stage turbocharging system is mainly affected by the matching speed and the bypass flow rate ratio. The validation results of the GT-Power model show that the plateau adaptability of the matched regulated two-stage turbocharging system can be investigated effectively using the equivalent matching model. Therefore, the equivalent matching model can be utilized to achieve a reasonable selection of the matching speed and it can simplify the matching problem of the regulated two-stage turbocharging system at different altitudes.

Establishment of a Two-Stage Turbocharging System Model and Analysis on Influence Rules of Key Parameters

“…Considering the two-stage turbocharging system as a single-stage turbocharging system, the relationship between the turbine front pressure, P T , and the total efficiency of the turbocharger, η Tb , is obtained from the power balance relational Expression (11) between the turbine and the compressor.…”

“…The error is within 3.5%, which proves that the optimized matching method adopted by the two-stage turbocharger in this paper meets the target pressure ratio requirement. Figures [10][11][12] show the comparison between the experimental data and simulation results of the external characteristic of the two-stage turbocharged engine. The error is within 3.5%, which proves that the optimized matching method adopted by the two-stage turbocharger in this paper meets the target pressure ratio requirement.…”

“…Liu et al [9] and Sanaye et al [10] also considered the influence of two-stage turbocharging distribution and turbine flow on the basis of the former and established a turbocharger calculation model and genetic algorithm (GA) optimization technology. Compared with the conventional methods, the matching method enables the matching points under different operating conditions to be located in a more reasonable area on the compressor map Li [11], Fenghua [12], and Shi et al [13] carried out theoretical research on the matching problem of an adjustable two-stage turbocharging system at different altitudes. Through the theoretical analysis of the adjustable two-stage turbocharging system, the equivalent matching model of the turbocharging system and the diesel engine is established, which provides abundant data for studying the matching model of a turbocharged engine at different altitudes.…”

Turbocharging strategy among variable geometry turbine, two-stage turbine, and asymmetric two-scroll turbine for energy and emission in diesel engines

“…The 2ST is another advanced turbocharging technology to decrease fuel consumption and pollutant emissions and simultaneously increasing engine output torque and power. 27 The 2ST system has two turbines with different throat areas, and it can achieve enough boost-pressure and decrease pumping loss through exhaust flow distribution. 28 The HP stage and the LP stage are connected sequentially and regulated via a by-pass valve.…”

Influence of varying altitudes on matching characteristics of the Twin-VGT system with a diesel engine and performance based on analysis of available exhaust energy

“…The total available flow energy is more sensitive to HP turbine, and the energy split to the low-pressure (LP) turbine is more sensitive to the altitudes. Li et al 11 studied the relationship between available flow energy and altitudes and turbine effective flow area and designed an equivalent matching model to solve the matching problems of TST with diesel engines at different altitudes. However, the bypass valve of TST only works at medium- and high-speed operation, and available exhaust energy and global expansion ratio (GER) cannot be effectively allocated between HP and LP turbines under low speeds at high altitudes.…”