Traditionally, the design of cooling systems for off-road machines has relied on steadystate and quasi steady-state cooling system models. Performance characteristics of cooling modules are obtained from tests under steady-state conditions, and analysis methods assume worst-case heat loads, which leads to cooling package over-design. Transient heat exchanger and temperature probe models have been developed and validated to enable transient cooling simulation for optimal cooling pack design, and engine control development and operation. These generic components, which are based on a simple heat transfer formulation and lumped thermal masses, were found to be suitable for the simulation of thermal transients through a representative machine work cycle. For a simple transient CAC model, consisting of three lumped thermal masses, the appropriate total mass in the model was found to be a proportion of the actual core mass of the physical component (∼42%). Of this lumped mass, the majority should be applied on the hot-side charge path (∼63%). As the fidelity of the model is increased, i.e. greater discretisation of thermal inertia, the required mass in simulation is expected to converge to that of the physical component. Transient thermal effects have been found to be significant on off-road machines. Accounting for thermal inertia in the CAC and fuel cooler improved fluid temperature response accuracy by ∼70% compared to a quasi steady-state model, for the fully warm machine work cycle that was considered. On the same cycle, the impact on accuracy was found to be less pronounced for the lubrication oil cooler, transmission oil cooler and radiator. Probes used to measure fluid temperature on off-road machines, do not respond fast enough to capture important temperature transients. The transient probe model that was developed enables tuning of transient machine models based on experiment, and is a key component for the development and implementation of optimised fluid temperature-based control strategies.
Cooling system simulation for an off-road machine under transient conditions
2013
18 Seiten, 13 Bilder, 2 Tabellen, 5 Quellen
Conference paper
English
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