Boost Drive Shaft

Boost drive shaft speed

Libraries:
Powertrain Blockset / Propulsion / Combustion Engine Components / Boost

Description

The Boost Drive Shaft block uses the compressor, turbine, and external torques to calculate the drive shaft speed. Use the block to model turbochargers and superchargers in an engine model.

You can specify these configurations:

Turbocharger — Connect the compressor to the turbine
- Two-way ports for turbine and compressor connections
- Option to add an externally applied input torque
Compressor only — Connect the drive shaft to the compressor
- Two-way port for compressor connection
- Externally applied input torque
Turbine only — Connect the drive shaft to the turbine
- Two-way port for turbine connection
- Externally applied load torque

For the Turbine only and Turbocharger configurations, the block modifies the turbine torque with a mechanical efficiency.

Equations

The Boost Drive Shaft block applies Newton’s Second Law for Rotation. Positive torques cause the drive shaft to accelerate. Negative torques impose a load and decelerate the drive shaft.

The block also calculates the power loss due to mechanical inefficiency.

Calculation	Equations
Shaft dynamics	$\frac{d ω}{d t} = \frac{1}{J_{s h a f t}} (η_{m e c h} τ_{t u r b} + τ_{c o m p} + τ_{e x t})$ with initial speed ω₀
Speed constraint	$ω_{m i n} \leq ω \leq ω_{m a x}$
Power loss	${\dot{W}}_{l o s s} = ω τ_{t u r b} (1 - η_{m e c h})$

Power Accounting

For the power accounting, the block implements these equations.

Bus Signal			Description	Equations
`PwrInfo`	`PwrTrnsfrd` — Power transferred between blocks Positive signals indicate flow into block Negative signals indicate flow out of block	`PwrCmpsr`	Shaft power from compressor	$τ_{c o m p} ω$
		`PwrTurb`	Shaft power from turbine	$τ_{t u r b} ω$
		`PwrExt`	Externally applied power	$τ_{e x t} ω$
	`PwrNotTrnsfrd` — Power crossing the block boundary, but not transferred Positive signals indicate an input Negative signals indicate a loss	`PwrMechLoss`	Mechanical power loss	$- {\dot{W}}_{t u r b}$
	`PwrStored` — Stored energy rate of change Positive signals indicate an increase Negative signals indicate a decrease	`PwrStoredDriveshft`	Rate change in rotational kinetic energy	$(η_{m e c h} τ_{t u r b} + τ_{c o m p} + τ_{e x t}) ω$

The equations use these variables.

ω	Shaft speed
ω₀	Initial drive shaft speed
ω_min	Minimum drive shaft speed
ω_max	Maximum drive shaft speed
J_shaft	Shaft inertia
η_max	Mechanical efficiency of turbine
τ_comp	Compressor torque
τ_turb	Turbine torque
τ_ext	Externally applied torque.
${\dot{W}}_{l o s s}$	Power loss due to mechanical inefficiency

Examples

Build Conventional Vehicle Model

Build a vehicle with an internal combustion engine using the conventional vehicle reference application.

Ports

Input

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Cmprs — Compressor torque
two-way connector port

Compressor torque, τ_comp, in N·m.

Dependencies

To create this port, for the Configuration parameter, select Turbocharger or Compressor only.

Turb — Turbine torque
two-way connector port

Turbine torque, τ_turb, in N·m.

Dependencies

To create this port, for the Configuration parameter, select Turbocharger or Turbine only.

ExtTrq — Externally applied torque
`scalar`

Externally applied torque, τ_ext, in N·m.

Dependencies

For turbocharger configurations, to create this port, set Additional torque input to External torque input.

Output

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Info — Bus signal
bus

Bus signal containing these block calculations.

Signal			Description	Units
`DriveshftSpd`			Shaft speed	rad/s
`MechPwrLoss`			Mechanical power loss	W
`ExtTrq`			Applied external torque	N·m
`PwrInfo`	`PwrTrnsfrd`	`PwrCmpsr`	Shaft power from compressor	W
		`PwrTurb`	Shaft power from turbine	W
		`PwrExt`	Externally applied power	W
	`PwrNotTrnsfrd`	`PwrMechLoss`	Mechanical power loss	W
	`PwrStored`	`PwrStoredDriveshft`	Rate change in rotational kinetic energy	W

Cmprs — Compressor speed
two-way connector port

Compressor speed, ω, in rad/s.

Dependencies

To create this port, for the Configuration parameter, select Turbocharger or Compressor only.

Turb — Turbine speed
two-way connector port

Turbine speed, ω, in N·m.

Dependencies

To create this port, for the Configuration parameter, select Turbocharger or Turbine only.

Parameters

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Block Options

Configuration — Specify configuration
`Turbocharger` (default) | `Turbine only` | `Compressor only`

Dependencies

Selecting Turbocharger or Compressor only creates the Cmprs port.
Selecting Turbocharger or Turbine only creates the Turb port.

Additional torque input — Specify external torque input
`External torque input` (default) | `No external torque`

Dependencies

To enable this parameter, select a Turbocharger configuration.
To create the Trq port, select External torque input.

Shaft inertia, J_shaft — Inertia
`1.55e-5` (default) | `scalar`

Shaft inertia, J_shaft, in kg·m^2.

Initial shaft speed, w_0 — Speed
`1000` (default) | `scalar`

Initial drive shaft speed, ω₀, in rad/s.

Min shaft speed, w_min — Speed
`100` (default) | `scalar`

Minimum drive shaft speed, ω_min, in rad/s.

Max shaft speed, w_max — Speed
`20000` (default) | `scalar`

Maximum drive shaft speed, ω_max, in rad/s.

Turbine mechanical efficiency, eta_mech — Efficiency
`0.95` (default) | `scalar`

Mechanical efficiency of turbine η_max.

Dependencies

To enable this parameter, select the Turbocharger or Turbine only configuration.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2017a

Boost Drive Shaft

Description

Equations

Power Accounting

Examples

Build Conventional Vehicle Model

Ports

Input

Cmprs — Compressor torque two-way connector port

Dependencies

Turb — Turbine torque two-way connector port

Dependencies

ExtTrq — Externally applied torque scalar

Dependencies

Output

Info — Bus signal bus

Cmprs — Compressor speed two-way connector port

Dependencies

Turb — Turbine speed two-way connector port

Dependencies

Parameters

Configuration — Specify configuration Turbocharger (default) | Turbine only | Compressor only

Dependencies

Additional torque input — Specify external torque input External torque input (default) | No external torque

Dependencies

Shaft inertia, J_shaft — Inertia 1.55e-5 (default) | scalar

Initial shaft speed, w_0 — Speed 1000 (default) | scalar

Min shaft speed, w_min — Speed 100 (default) | scalar

Max shaft speed, w_max — Speed 20000 (default) | scalar

Turbine mechanical efficiency, eta_mech — Efficiency 0.95 (default) | scalar

Dependencies

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using Simulink® Coder™.

Version History

See Also

Cmprs — Compressor torque
two-way connector port

Turb — Turbine torque
two-way connector port

ExtTrq — Externally applied torque
`scalar`

Info — Bus signal
bus

Cmprs — Compressor speed
two-way connector port

Turb — Turbine speed
two-way connector port

Configuration — Specify configuration
`Turbocharger` (default) | `Turbine only` | `Compressor only`

Additional torque input — Specify external torque input
`External torque input` (default) | `No external torque`

Shaft inertia, J_shaft — Inertia
`1.55e-5` (default) | `scalar`

Initial shaft speed, w_0 — Speed
`1000` (default) | `scalar`

Min shaft speed, w_min — Speed
`100` (default) | `scalar`

Max shaft speed, w_max — Speed
`20000` (default) | `scalar`

Turbine mechanical efficiency, eta_mech — Efficiency
`0.95` (default) | `scalar`

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.