Automotive Turbocharger

Turbocharged Internal Combustion (IC) Engine Model

Open the waste gate too slowly, or inject gases from an EGR too quickly, and the compressor will surge, overloading the intercooler with warmer air without a corresponding increase in pressure (not to mention noise).  Open the waste gate too quickly, or fail to get exhaust gases to the turbine fast enough, and the boost lags and the compressor might even choke when it fails to meet a sudden engine demand.

And those are just some of the transient interactions between the turbocharger and the engine. Before you can get to that point, you have to first design a compressor, turbine, and intercooler that are well matched to the engine over a wide range of operating conditions, probably assuming perfect or instantaneous controls as a starting point.

Two sample FloCAD models were built to explore both

  • short time-scale events such as pressure waves within intake and exhaust runners (Detailed-level, applicable for valve or control system stability investigations), and
  • long time-scale events such as boost lag (System-level, including steady-state solutions for rapid sizing).

These models illustrate key program features and capabilities, but they may also be used as templates for other engine and compressor/turbine design studies.

A library of six turbine and five compressor designs was constructed as part of these models, and the development of those turbomachine designs is also summarized.

Click here to download this sample from our support forum

The development of this sample model spawned of another IC Engine sample model designed to explore fast‐transient interactions within an engine.

 

Chart of Turbocharger Shaft Speed Lagging a Transient Engine Acceleration

Turbocharger Shaft Speed Lagging a Transient Engine Acceleration

 

Chart of Waste-gate and Pop-off Valve Responses to the Engine Acceleration Event

Waste-gate and Pop-off Valve Responses to the Engine Acceleration Event

 

Parametric Sweeps of Net Torque on Turbocharger Shaft to Find Steady Operating Points

Parametric Sweeps of Net Torque on Turbocharger Shaft to Find Steady Operating Points.

 

Postprocessed Sinaps® Diagram showing Temperatures and Flows for Detailed Model

Postprocessed 2D-sketch Mode FloCAD® Diagram showing Temperatures and Flows for Detailed Model

 

Chart of Pressures in the Intake and Exhaust Systems During One cam shaft Revolution

Pressures in the Intake and Exhaust Systems (for Cylinder #1, 3000 rpm) During One cam shaft Revolution (TDC at left, center, and right of plot)

 

dispersed vs. coalesced front

Tuesday, June 26, 2018, 1-2pm PT, 4-5pm ET

This webinar describes flat-front modeling, including where it is useful and how it works. A flat-front assumption is a specialized two-phase flow method that is particularly useful in the priming (filling or re-filling with liquid) of gas-filled or evacuated lines. It also finds use in simulating the gas purging of liquid-filled lines, and in modeling vertical large-diameter piping.

Prerequisites: It is helpful to have a background in two-phase flow, and to have some previous experience with FloCAD Pipes.

Register here for this webinar

FloCAD model of a loop heat pipe

Since a significant portion of LHPs consists of simple tubing, they are more flexible and easier to integrate into thermal structures than their traditional linear cousins: constant conductance and variable conductance heat pipes (CCHPs, VCHPs). LHPs are also less constrained by orientation and able to transport more power. LHPs have been used successfully in many applications, and have become a proven tool for spacecraft thermal control systems.

However, LHPs are not simple, neither in the details of their evaporator and compensation chamber (CC) structures nor in their surprising range of behaviors. Furthermore, there are uncertainties in their performance that must be treated with safety factors and bracketing methods for design verification.

Fortunately, some of the authors of CRTech fluid analysis tools also happened to have been involved in the early days of LHP technology development, so it is no accident that Thermal Desktop ("TD") and FloCAD have the unique capabilities necessary to model LHPs. Some features are useful at a system level analysis (including preliminary design), and others are necessary to achieve a detailed level of simulation (transients, off-design, condenser gradients).

CRTech is offering a four-part webinar series on LHPs and approaches to modeling them. Each webinar is designed to be attended in the order they were presented. While the first webinar presumes little knowledge of LHPs or their analysis, for the last three webinars you are presumed to have a basic knowledge TD/FloCAD two-phase modeling.

Part 1 provides an overview of LHP operation and unique characteristics
Part 2 introduces system-level modeling of LHPs using TD/FloCAD.
Part 3 covers an important aspect of getting the right answers: back-conduction and core state variability.
Part 4 covers detailed modeling of LHPs in TD/FloCAD such that transient operations such as start-up, gravity assist, and thermostatic control can be simulated.